planner: fix the bug that wrong collation is used when try fast path for enum or set

expression/integration_test.go

@@ -6301,6 +6301,15 @@ func (s *testIntegrationSerialSuite) TestCollationBasic(c *C) {
 	tk.MustQuery("select a from t_ci where a='A'").Check(testkit.Rows("a"))
 	tk.MustQuery("select a from t_ci where a='a   '").Check(testkit.Rows("a"))
 	tk.MustQuery("select a from t_ci where a='a                    '").Check(testkit.Rows("a"))
+
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(c set('A', 'B') collate utf8mb4_general_ci);")
+	tk.MustExec("insert into t values('a');")
+	tk.MustExec("insert into t values('B');")
+	tk.MustQuery("select c from t where c = 'a';").Check(testkit.Rows("A"))
+	tk.MustQuery("select c from t where c = 'A';").Check(testkit.Rows("A"))
+	tk.MustQuery("select c from t where c = 'b';").Check(testkit.Rows("B"))
+	tk.MustQuery("select c from t where c = 'B';").Check(testkit.Rows("B"))
 }
 
 func (s *testIntegrationSerialSuite) TestWeightString(c *C) {

planner/core/point_get_plan.go

@@ -1100,7 +1100,8 @@ func getNameValuePairs(stmtCtx *stmtctx.StatementContext, tbl *model.TableInfo,
 			}
 		}
 		// The converted result must be same as original datum.
-		cmp, err := d.CompareDatum(stmtCtx, &dVal)
+		// Compare them based on the dVal's type.
+		cmp, err := dVal.CompareDatum(stmtCtx, &d)
 		if err != nil {
 			return nil, false
 		} else if cmp != 0 {